Firefighters were called to the 900 block of West Cambria Street shortly after midnight. They found heavy fire coming from the second floor.
It took them about a half hour to get the upper hand.
Police say the 2-story house was abandoned and may have been used by squatters.
One woman - a neighbor who became short of breath - was taken to an area hospital in stable condition.
Action News is told that PECO is investigating reports of an illegal electrical hookup.
Fire investigators are working to determine what sparked the blaze.